LILE
As LILE in are Petrology lithophile elements with large ionic radius designated, usually by their incompatibility distinguished during crystallization of Lithosphärenschmelzen and in the melt remain.
designation
The acronym LILE (sometimes just LIL) is derived from English and stands for large-ion lithophile elements - in German lithophile elements with large ionic radii .
Lithophilic elements such as rubidium , strontium , barium , niobium , tantalum , thorium , uranium and rare earths have an affinity for silicate rocks , in contrast to siderophilic elements such as iron , cobalt , osmium , iridium or nickel , which prefer metal phases or chalcophilic elements such as sulfur , Selenium , cadmium , arsenic , copper or zinc , which can be found in sulphide phases .
LILE are sometimes also referred to as LFS ( low field strength ) or LFSE, i.e. H. Elements with low field strength. The field strength or the ion potential (engl. Ionic potential ) is defined as the ratio of charge / radius (Z / r). The delimitation of the LILE from the HFSE is along the straight line Z / r = 2 (with Z = 1, 2,… and r in 10 −10 m or Å). For LILE, Z / R <2 and for HFSE Z / r> 2.
Members
The following elements with an ionic charge of +1 and +2 are included in the LILE :
- monovalent elements:
- two-valued elements:
Sometimes the +4-valent elements thorium (108 pm) and uranium (103 pm) are also classified under the LILE, although they actually belong to the HFSE.
Note: the elements strontium, barium and europium behave as compatible elements in acid magmas and accumulate in the crystallizing feldspars .
properties
In contrast to the immobile HFSE, LILE are very mobile elements in liquids and can easily be removed from the rock structure, for example by hydrothermal solutions in the course of metasomatic or metamorphic processes . This phenomenon has to be taken into account especially when analyzing rocks. Conversely, anomalies in the LILE system can provide valuable information about hydrothermal changes in mantle rocks , which would otherwise go unnoticed.
Initial definition
The term LILE was first introduced into the scientific literature by PW Gast in 1972. In its first definition, the rare earths, thorium and uranium were included. Gast also classified lithium under the LILE because of its relatively high ion potential, even if it only has a small ionic radius (82 pm). This practice is no longer followed, however, LILE should rather have larger ionic radii than Na + and Ca 2+ - the largest cations in rock-forming minerals. Even the rare earths are now usually no longer included in the LILE.
Individual evidence
- ↑ Shannon, RD: Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides . In: Acta Cryst. A. Band 32 , 1976, pp. 751-767 , doi : 10.1107 / S0567739476001551 .
- ^ Gast, PW: Limitations on the composition of the upper mantle . In: J. Geophys. Acta . tape 36 , 1972, p. 241-257 .